Yig resonator microstrip coupling device

ABSTRACT

A microstrip manifold providing a plurality of frequency selective outputs from a single input signal including a common input microstrip transmission line terminated at one end and a plurality of output microstrip transmission lines disposed substantially normal to the input transmission line and coupled thereto by means of respective yttrium iron garnet (YIG) sphere resonators, each being tuned to a predetermined resonant frequency by a separate magnetic field to provide isolation between each of the output transmission lines. Additionally, each of the output transmission lines are terminated at a short circuit in proximity to the respective YIG sphere. The input conductor is not grounded at the YIG spheres but is terminated at the end of the line.

United States Patent [72] Inventors Robert A. Moore Severna Park;Theodore M. Nelson, Catonsvllle; James M. Fhherty, Catonnvllle, all ofMr].

[Zl] Appl. No. 889,514

[22] Filed Dec. 31, I969 451 Patented on. s, 1971 73] AssigneeWestinghouse Electric Corporation Pittsburgh, Pa.

50 Field olSeareh 333/l.l,6, 10, 24.2, 73, 73 c, 73 s, 73 w [56]RelerencesClted UNITED STATES PATENTS 2,816,270 12/1957 Lewis, 3; 3 7 wx Primary Examiner-Herman Karl Saalbach Assistant ExaminerPaul L.Gensler Attorneyr- F. H. Henson, E. P. Klipfel and J. L. WiegretfeABSTRACT: A microstrip manifold providing a plurality of frequencyselective outputs from a single input signal including a common inputmicrostrip transmission line terminated at one end and a plurality ofoutput microstrip transmission lines disposed substantially normal tothe input transmission line and coupled thereto by means of respectiveyttrium iron garnet (YIG) sphere resonators, each being tuned to apredetermined resonant frequency by a separate magnetic field to provideisolation between each of the output transmission lines. Additionally,each of the output transmission lines are terminated at a short circuitin proximity to the respective YlG sphere. The input conductor is notgrounded at the YIG spheres but is terminated at the end of the line.

l8 SIGNAL 2 l SIGNAL OUT l SIGNAL OUT PATENTED UN 5 B?! SHEET 2 [IF 2 TT RooR TEMPERATURE 6 (LINEAR (FILTER BANK] POLARIZATION I |ooc [FILTERBANK) 5 f 4 ROOM TEMPERATURE 5 POLAR'ZAT'OM |00C(SINGLE FILTER] E 2 LL!2 0 l l 1 1 FIG-4 .2 l3 .4 R gr 20 1 E r. FIGS -5-4-3-2|o|2345 ONE HALFRESONATOR BANDWIDTHS Bl36-VA6 YIG RESONATOR MICROS'I'RIP COUPLING DEVICEThe invention herein described was made in the course of or under acontract or subcontract thereunder the Department of the Air Force perAF l9(628)5 l 67.

BACKGROUND OF THE INVENTION l. Field of the Invention This inventionrelates generally to the field of microwave energy transmissionapparatus and more particularly to an electronically tunable manifoldcoupler having a single input transmission line and a plurality offrequency responsive output channels employing YiG resonators tuned toselected frequencies by means of respective unidirectional magneticfields.

2. Description of the Prior Art Frequency selective waveguide couplingdevices having ferrite elements biased to difierent resonant frequenciesare disclosed in U.S. Pat. No. 3,214,519 issued to L. Nathanmn.Magnetically tunable band-stop and band-pass filters including YlGresonators in combination with stripline apparatus are disclosed in U.S.Pat. No. 3,268,838 issued to G. L. Matthaei. Also a YlG preselector isdisclosed in U.S. Pat. No. 3,299,376 issued to R. Blau, et al.Additional prior art disclosing various embodiments of YlG filters arethe following: U.S. Pat. No. 3,290,625, to R. .l. Bartram, et al. U.S.Pat. No. 3,368,169, to R. S. Caner, et al. U.S. Pat. No. 3,426,297, toM. Cohen; and U.S. Pat. No. 3,435,385, to M. Cohen.

The prior art requires the use of a circularly polarized input signal ora grounded termination of the input transmission line at the YIGresonator. Both of these requirements in the embodiments disclosedpreclude the provision of multiple output channels coupled to a singleinput channel. The present inven tion provides for coupling of aplurality of YIG resonators to the input channel wherein neithercircularly polarized energy nor a shorted terminal input terminalimmediately at each of the YIG resonators is required.

SUMMARY Briefly, the subject invention is directed to a manifold couplerfor microwave electromagnetic energy wherein .a plurality of frequencyselective outputs is obtained from a single transmitted input signal andcomprises, inter alia, an input microstrip transmission line coupled atone end to a source f microwave energy and terminated at its other endby a predetermined impedance connected to a point of referencepotential. A plurality of output microstrip transmission lines areparallely disposed transverse to the input transmission line andseparated therefrom by a ground plane. Each of the plurality of outputtransmission lines is terminated at one end by a short circuit in theground plane. The ground plane contains an opening or an iris betweeneach of the output transmission lines and the transverse inputtransmission line wherein a YlG sphere is located. The YIG sphereadditionally is in close proximity to the short circuit termination ofthe respective output transmission line. A separate magnetic field isapplied through each of the YlG sphere elements to separately resonateeach of the V16 spheres to a predetermined frequency whereby each of theoutput transmission lines transmit separate frequency signals withoutinteraction between adjacent output transmission lines or channels. Themagnetic field is applied through each of the '10 spheres by means of aseparate magnet located above the respective output transmission line inproximity to the iris and the sphere contained therein.

BRIEF DESCRIPTION OF THE DRAWINGS F 1G. I is an exploded perspectiveview of the preferred embodiment of the subject invention;

FIG. 2 is a fragmentary top view of the preferred embodiment of thesubject invention;

FIG. 3 is a cross-sectional view of the embodiment shown in FIG. 2 takenalong the lines 3-3;

FIG. 4 is a diagram illustrative of the insertion loss vs. frequencycharacteristic of the subject invention; and

FIG. 5 is a diagram illustrative of the obtainable bandwidthcharacteristics from the subject invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Before proceeding to a detaileddescription of the subject invention. it should be pointed out thatferrite resonators in the form of a sphere of yttrium iron garnet (YIG)are well known to those skilled in the art. These elements comprisehighly polished single crystals having a narrow line width in theneighborhood of 0.3 to 0.5 oersteds. These elements, moreover areavailable commercially and are fabricated from a single crystal by atumbling process in which successively finer and finer grits are used.Although the orientation of the crystallographic axis of the elementsaffects the frequency response, this is not of primary significance inthe device comprising the subject invention. A more detailed explanationof the crystal structure and the nomenclature used to define it can befound in "Introduction to Solid State Phyics" by Kittie (John Wiley andSons, inc., 1953).

The ferrite elements act as they do because of Larmor recession. That isto say the electrons in the ferrites have a magnetic moment or spin andbecause of this spin, tend to precess when subjected to the action of aDC field. The plane of this processional movement, moreover, is at rightangles to the field lines. For example, consider a YlG spherical elementsituated at the origin of a X-Y-Z coordinant system wherein RF energy iscoupled in along the X-axis and coupled out along the Y-axis Thefrequency at which coupling will occur from the input to the outputdepends upon the magnitude of the unidirectional or DC magnetic fielddirected along the Z- axis When the YIG sphere is not magnetized, thereis no power transfer between the axes. When a DC magnetic fieldindicated by the arrow H in FIG. I, is applied along the Z-axis theorthogonal E-vector of the input RF energy causes the electrons in theYIG sphere to precess around the Z-axis This produces of RF magneticmovement along the Y-axis to induce a voltage therein. Precession for aYIG sphere is strongest at ferrimagnetic resonance and coupling frominput to output is also strongest at resonance. Coupling varies ofiresonance as detennined by the degree of coupling of the input andoutput to the YIG sphere. Thus the loaded 0 of such a device isdetermined not only by the unloaded Q of the YIG material, but by thetightness of the coupling between the input and the output. It has beenobserved that increasing 0 makes possible an approximate constantbandwidth as a function of frequency.

Referring to the drawings, the apparatus comprising the subjectinvention as disclosed in FIGS. I, 2 and 3 includes an input microstriptransmission line I0 comprised of a strip of current conducting materialdisposed on a dielectric member 12 which may be, for example, a sheet ofalumina having a predetermined thickness. The input transmission lineIt) is disposed on one outer surface 13 of the dielectric member 12 andextends the entire length thereof to provide a first and a secondterminal end 14 and 16, respectively as shown by FIG. 2. Coupled to theterminal ends I4 and 16 are a pair of RF connectors 18 and 20. The RFconnector II is adapted to receive an input microwave signal. The RFconnector 20 is adapted to be coupled to a suitable RF termination 22.which may be, for example, a dummy load, or the like and which is shownschematically as a load impedance connected to a point of referencepotential illustrated as ground. A second dielectric member 24 similarto the first dielectric member 12 and having substantially the samedimensions such as length, width and thickness includes a plurality ofoutput microstrip transmission lines 26 of current conducting materialdisposed in substantially parallel relationship on one outer surface 27of the layer 24 as shown by FIGS 1 and 2. The outer ends 28 of thetransmission lines 26 terminate at the edge of the insulating layer 24while the other ends 30 of the lines 26 extend through the openings orholes 32 through the entire thickness of the dielectric member 24 to themutually opposite surface 33 as shown by FIG. 3, where they terminate ina metal ground plane 34. Moreover, the output microstrip transmissionlines 26 cross the input transmission line at substantially rightangles. The metal ground plane 34 as shown by FIG. 3 separates thedielectric members 12 and 24 and is contiguous with the surfaces and 33thereof which are seen to be opposite from the surfaces containing theinput transmission line 10 and the plurality of output transmissionlines 26. The metal ground plane 34 has substantially the same lengthand width dimensions of the insulated layers 12 and 2A and iselectrically common to the point of ground reference potential. Themetal ground plane 34 ha a predetermined thickness and includes aplurality of round apertures or irises 36 corresponding in number to theplurality of output transmission lines 26. Moreover. the irises 36 arerespectively located at a point directly beneath the output transmissionlines 26 and directly above the input transmission line 10 such that theplurality of irises 36 are substantially in line with the length ofconducting material forming the input transmission line 10. A sample offerrimagnetic material comprised of a single crystal garnet compoundsuch as yttrium iron garnet (YIG) in the form of a sphere 38 is locatedwithin each of the irises 36 between the input transmimion line 10 andthe respective output transmission line 26. When desirable galliumyttrium iron garnet (GaYIG) may be used. This is shown by means of theexploded perspective view of FIG. I and the cross sectional view thereofas shown by FIG. 3.

While the configuration thus described comprises the preferredembodiment of the invention, two other forms of TEM transmission linee.g. coaxial and stripline could be used when desirable. Also anotherembodiment visualized consists in a configuration wherein all of theconductors are on one surface rather than being disposed on both sidesof the ground plane.

Associated with each of the YIG spheres 38 is a respective circularpermanent magnet which is situated over each of the output transmissionlines 26 so that its magnetic I-I-field intersects the YIG sphereorthogonally with respect to the direction of the electric field of theRF energy which would exist in the input transmission line 10 in theplurality of parallel output transmission line III in the plurality ofparallel output transmission lines 26. This is disclosed with referenceto the exploded view of the present invention as disclosed by FIG. I andthe fragmentary top view thereof as shown in FIG. 2. Although apermanent magnet is shown, any type of apparatus for generating aunidirectional magnetic field may be utilized.

The plurality of output transmission lines 26 are shorted to the groundplane 34 through the holes 32 in the second insulating layer 24 as shownin FIG. 3. It should be pointed out, however, that this termination ispreferably less than a quarter of a wavelength from the YIG spheres 38of the range of frequencies being transmitted in the input transmissionline 10. The magnitude of the magnetic field H of each of the magnets 40selectively establish a resonant frequency of the respective YIG spheres38 so that each of the plurality of output transmission lines 26 haveenergy coupled thereto from the input transmission at the respectiveresonant frequency of its YIG sphere 38. Thus each of the YIG spheres 38couples to the input transmission line 10 at its resonant frequencywhile leaving energy undisturbed at other frequencies.

By coupling the terminated input transmission line 10 to a single sourceof microwave energy having a spectrum of various frequencies, thesubject invention will selectively channel certain selected frequencieson each of the output transmission lines 26, thereby providing a RFmanifold of microwave energy.

While the reference to prior art devices normally utilize circularlypolarized electromagnetic energy or a grounded termination of the inputline at the resonator for obtaining resonant coupling from an inputtransmission line to an output transmission line by means of a YlGresonator, it has been observed that the subject invention as embodiedby the configuration shown in FIGS. 1-3 is operable with a linearlypolarized energy input with a substantial transfer to the plurality ofparallel output transmission line strips 26 with only an approximately 3db. insertion loss as evidenced by FIG. 4 which dis- 5 closes theinsertion loss for both linear and circular polarization at roomtemperature and 100' C. operating between the frequency range of l to1.5 GHz (IXIO' Hz.). Although the data for FIG. 4 was obtained foroperation in the frequency range of l.0 to 1.5 GHz, by utilizing GaYIGas the resonators l0 operation can be achieved covering the frequencyrange from below 200 MHz to above l.8 Gl-Iz; however, theexact insertionloss and bandwidth characteristics will depend upon the actual frequencyrange utilized.

Each of the resonantly tuned YIG spheres 38 act as a 15 frequency filterso that selective tuning of each of the output channels by means of itsrespective magnet 40 can produce a filter bank having frequencycharacteristics such as shown by FIG. 5a and 5b. Both sets of curvesdisclose a tuning of each of the YIG spheres 38 to provide a series offilters which exhibit frequency overlap. For example. FIG. 5a disclosesa bandwidth characteristic of a single tuned filter whereas FIG. 5bdiscloses a bandwidth characteristic for double tuned filter.

What has been shown and described, therefore, is a manifold directionalcoupler providing selective coupling between a single input line and aplurality of output channel lines by means of respective tuned YIGresonators.

What is claimed is:

1. A manifold for microwave energy providing a plurality of frequencyselective output signals from a single input signal comprising incombination:

a common input transmission line for microwave energy including means onone end adapted to receive an input signal and means terminating theother end in a predetermined load;

at least three output transmission lines of microwave energy coupled tosaid input transmission line intermediate the ends thereof;

a ferrimagnetic resonator coupling each of said plurality of 40 outjputtransmission lines to said input transmission line;

means generating unidirectional magnetic fields of different intensitythrough the respective fcrrimagnetic resonators for selectively tuningeach resonator so that it is resonant to a selected frequency band ofthe frequencies included in said input signal and means terminating eachof said output transmission lines in a short circuit in proximity to itsrespective fcrrimagnetic resonator.

2. Apparatus for manifold coupling microwave energy from a common inputsource to a plurality of output channels comprising in combination:

a first dielectric member; an input strip-transmission line forelectromagnetic energy located on one surface of said first dielectricmember;

a metallic ground plane having one surface contiguous with the oppositesurface of said first dielectric member and having a plurality ofapertures therein located in proximi ty to and along the direction ofsaid input strip-transmission line;

a respective ferrimagnetic resonator located in each of said pluralityof apertures;

a second dielectric member having one surface contiguous with theopposite surface of said metallic ground plane; a plurality of outputstrip-transmission lines located on the opposite surface of said seconddielectric member traversing a respective aperture of said plurality ofapertures substantially at right angles to said input strip-transmissionline and having one end thereof terminated in a short circuit connectionto said ground plane at a predetermined distance from the respectiveferrimagnetic resonator; and

means for establishing unidirectional magnetic fields of dif ferentintensity through the respective ferrimagnetic resonators to establishrespectively selected gyromagnetic resonant frequencies in saidchannels.

3. The invention as defined by claim 2 and wherein said plurality ofapertures are comprised of substantially round irises.

4. The invention as defined by claim 2 wherein said ferrimagneticresonator comprises a sphere of ferrimagnetic material.

5. The invention as defined by claim 4 wherein said ferrimagneticmaterial comprises a single crystal gamet compound.

6. The invention as defined by claim 4 wherein said ferrimagneticmaterial comprises yttrium iron garnet.

7. The invention as defined by claim 2 and additionally including atransmission line termination coupled to one end of said inputstrip-line transmission line.

8. The invention as defined by claim 7 wherein said transmission-linetermination comprises impedance coupled from said one end of the inputstrip-transmission line to a point of reference potential common to saidground plane.

9. The invention as defined by claim 2 wherein said plurality of outputstrip-transmission lines are substantially mutually parallel to eachother.

10. The invention as defined by claim 9 wherein said plurality ofsubstantially parallel output strip-transmission lines have one endthereof extending through said dielectric member.

11. The invention as defined by claim 10 wherein said ferrimagneticresonator comprises a YlG sphere.

2. Apparatus for manifold coupling microwave energy from a common input source to a plurality of output channels comprising in combination: a first dielectric member; an input strip-transmission line for electromagnetic energy located on one surface of said first dielectric member; a metallic ground plane having one surface contiguous with the opposite surface of said first dielectric member and having a plurality of apertures therein located in proximity to and along the direction of said input strip-transmission line; a respective ferrimagnetic resonator located in each of said plurality of apertures; a second dielectric member having one surface contiguous with the opposite surface of said metallic ground plane; a plurality of output strip-transmission lines located on the opposite surface of said second dielectric member traversing a respective aperture of said plurality of apertures substantially at right angles to said input strip-transmission line and having one end thereof terminated in a short circuit connection to said ground plane at a predetermined distance from the respective ferrimagnetic resonator; and means for establishing unidirectional magnetic fields of different intensity through the respective ferrimagnetic resonators to establish respectively selected gyromagnetic resonant frequencies in said channels.
 3. The invention as defined by claim 2 and wherein said plurality of apertures are comprised of substantially round irises.
 4. The invention as defined by claim 2 wherein said ferrimagnetic resonator comprises a sphere of ferrimagnetic material.
 5. The invention as defined by claim 4 wherein said ferrimagnetic material comprises a single crystal garnet compound.
 6. The invention as defined by claim 4 wherein said ferrimagnetic material comprises yttrium iron garnet.
 7. The invention as defined by claim 2 and additionally including a transmission line termination coupled to one end of said input strip-line transmission line.
 8. The invention as defined by claim 7 wherein said transmission-line termination comprises impedance coupled from said one end of the input strip-transmission line to a point of reference potential common to said ground plane.
 9. The invention as defined by claim 2 wherein said plurality of output strip-transmission lines are substantially mutually parallel to each other.
 10. The invention as defined by claim 9 wherein said plurality of substantially parallel output strip-transmission lines have one end thereof extending through said dielectric member.
 11. The invention as defined by claim 10 wherein said ferrimagnetic resonator comprises a YIG sphere. 